Defogging glass plate

ABSTRACT

A defogging glass plate includes an electric heating element, such as being made of conductive films or electric resistance strips for electrically heating the glass plate, and a sensor having a pair of electrodes which are arranged in parallel with a suitable gap and which are fitted on the surface of the glass plate, for automatically controlling the application of heat to the glass plate depending on the cloudiness or visibility thereof.

United States Patent 11 1 Nagasima 1111 3,749,885 1451 July 31,1973

DEFOGGING GLASS PLATE Takeomi Nagasima, Yokohama, Japan Asahi Glass Company, Ltd., Tokyo, Japan Filed: Dec; 10, 1971 Appl. No.: 206,728

inventor:

[73] Assignee:

Foreign Application Priority Data Dec. 18, 1970 Japan 45/126498 us. 01 219/522, zoo/61.05, 219/203, 219/509, 340/235 1m. (:1. 1105b 3/06 Field f Search.... 219/202 203, 212, 219/494, 509, 522; 73/73, 340/234, '23s; ZOO/61.04, 61.05, 61.06; 15 250.05

References Cited UNITED STATES PATENTS 1/1971 Livingston et al. 219/522 9/1914 Stroud 340/235 Fiene .f. 340/235 2,064,651 12/1936 2,424,735 7/1947 Boothroyd... 314/235 X 2,617,972 11/1952 Nutter ZOO/61.05 X 3,127,485 3/1964 Vitolo ZOO/61,05 3,233,078 l/l966 Siemianowsky ZOO/61.05 X 3,412,326 11/1968 Jones et a]. 340/234 X 3,484,583 12/1969 Shaw, Jr. 219/522 FOREIGN PATENTS OR APPLICATIONS 727,020 3/1955 Great Britain 340/235 1,012,146 ,12 1965 Great Britain 340 235 I Primary Exainirirvolodymyr Y1 Maven/sky Attorney-Norman F. Oblon, Marvin J. Spivak et al.

[5 7 ABSTRACT A defogging glass plate includes an electric heating element, such as being made of conductive filmsor electric resistance strips for electrically heating the glass plate, and a sensor having a pair of electrodes which are arranged in parallel with a suitable-gap and which are fitted on the surface of the glass plate, for automaticallycontrolling the application of heat to the glass plate depending on the cloudiness or visibility thereof.

5 Claims, 3 Drawing Figures DETECTING [cmcun Z CONTROL 1 CIRCUIT I 30c POWER souacs mm ma 3.749.885

DETECTING (cmcun CONTROL 1 c|Rcu|T FL v I 'Koc POWER SOURCE FIG 5 p r 9 9 F!G.2

INVENTOR TMEOm mensmn BY m,

ATTORNEY BACKGROUND OF THE INVENTION.

1. Fieldof the Invention DETAILEDDESCRIPTION OF THE PREFERRED EMBODIMENTS Referring nowto the drawing wherein like reference This invention generally relates to a defogging glass numerals designate identic corresponding Parts plate, and more particularly to a defogging glass-plate having an electric resistance heating element which is automatically controlled in. accordance withthe amount of moisture onand hence. the visibility of the glass plate.

2. Description of the. Prior Art In the past, it was knownntoprint a glassplate with a conductive film onthe surface thereof or to provide an electric heating element, such as anelectric resistance strip, on a, glassplate for heating the glass plate so asto prevent cloudinesstof'the glass plate, causedby ice, frost, fog,. condensing moisture on'the surface of the glass plate orthe like,.so as to'maintain the transparency. andhence visibility of theglass plate;

While somewhat satisfactory,.in order to maintain the visibility of the conventional: galss plates such as used. in automobiles, aeroplanes, ships,other. vehicles, window glass plates for buildingsor other: various apparatus and the like, which has: an electric heatingelement therein, one had to continuosly observe the condition of the glass'plate in ordersto determine. whether the electric heating elementshouldbe manually activated. A need existed'therefore foanon-fog glassplate which could be automatically heatedby an electric.

heatingelement whenever visibility could be hampered by being coveredwith: moisture, and the like.

SUMMARY OF THE INVENTION Accordingly, it is an objectof this invention to provide a new and improved" unique glass plate havingan electric heating element which" is automatically heated by detecting moisture and which automatically removes any cloudiness on thesurfaceof the glassplate.

It is another object of thisinvention to provide a new andimproved unique. defogging glass plate havinga'stable and highly sensitive sensor for detecting: moisture condensed on the surface'of the'glass plates Briefly, in accordance. with this inventionthe foregoing and other objectsare' attained bytheprovisionof a defogging glass plate which includesan electric heating element, such asconductivefilms or electric resistance strips for electricallyheating the glass plate, and

a sensor havinga pair of electrodes which are arranged in parallel witha suitable gap, such as about 0.1 10.0 mm. and which is fitted on the surface of the glass plate, for automatically controllingthe heating thereof in response to any cloudiness-on the-glass plate.

BRIEF DESCRIPTION OF THE DRAWINGS" throughout the several views, and more particularly to FIG.. 1' thereof wherein an illustrative preferred embodiment of the defogging glass plate according to this invention is shown'as includinga glass plate 1, a plurality of electric resistance strips 2, a pair of bus bars 3 and3, a pair of terminalsd and 4', lead lines 5 and'S", a sensor 6, a detecting circuit 7 and a control circuit 8.

The plurality of electric resistance strips (or electroconductive lines) 2. are arranged on the glass plate i withsubstantially the same gap between each other. The pair of bus bars 3 and 3 have a relatively broad stripshape and are respectively connected'in parallel to the electric resistance strips 2, for enabling an electric current, such as a D. C. current, to be applied 0 thereto. The pair of bus bars 3 and 3' are further-cone nected'through a respective one of the terminals 4 and 4" and the leadwires 5 and 5 to the control circuit 8. The plurality of electricheating elements 2, such as the electroconductive lines-orthe electric resistance strips shown in FIG. 1, may suitably be made of an electroconductive material havng high adhesiveness, high abrasion resistance and high chemical stability.

It has been found preferable to use a ceramic electroconductive coating material for the electric resistance heatingelements-2 and the same may be made as fol lows. Anrelectroconductive frit is made of glass powder having alow melting point and fine particles of a conductive metal, such as silver. The electroconductivefrit is admixed andkneaded with an organic binder and the resulting. paste or suspension thereof I is printed or:

coated on the glass plate, such as by screemprinting. The printing .or coated glass plate is then heated at a high temperature to thereby form the electric resis tance heatingelements 2 on'the glass plate.

By way of example, typical commerical compositions used for preparing the ceramic electroconductive coating material areas follows:

COMPOSITION I INGREDIENT PERCENT BY I WEIGHT PbO 7.5 8,0, 1.0 SiO, l.5' Finelydivided silver 70.0 French Fat Oil 12.5 Turpentine 7.5

COMPOSITION 2 INGREDIENT PERCENTAGE BY I WEIGHT 1 Finely divided silver 72.6 vP 9.: SiO,' L7 1 ,0 7.5 Ethyl Alcohol 7.5

According to the present invention, itis also possible to insert a plurality ofelectric resistance wires, such as 'nickel-chromiumwires, between a plied glass plate and ingelements 2 should preferably be in the range of sub stantially 0.3 1.0 mm. Each gap between the printed lines or strips is preferably in a range of about 20-40 mm.

The sensor 6 is connected to the detecting circuit 7 which in turn is connected to the control circuit 8. The detecting circuit 7 will be closed by an actuation of the sensor 6, and the control circuit 8 will be actuated by an operation of the detecting circuit 7. When the sensor 6 is actuated the electric heating elements will be heated so as to remove any moisture on the surface of the glass plate 1.

The sensor 6 is fixed on the surface of the glass plate 1 and is shown with reference to FIG. 2 as including a pair of electrodes 9 and 9 each having a gap, such as in the range of about 0.1 10.0 mm., a pair of terminals 10 and 10' and a pair of lead wires 11 and 11'. The pair of lead wires 11 and 11' are connected to the detecting circuit 7. It should be understood that when the gap distance of the electrodes 9 and 9' is in the range of about 1 0.1 10.0 mm that the sensitivity of the sensor 6 is suitable for practical use. Thus, for example, if the gap is less than 0.1 mm, an electric current will leak between the electrodes in response to the condensing of a small amount of moisture such that the sensitivity of the sensor is too high for practical use. On the other hand, if the gap distance is higher than 10.0 mm, the sensitivity of the sensor will be too low for practical use. The invention is not limited to the use of a single pair of electrodes and alternatively, additional pairs of electrodes can be used in the sensor.

Thus, a typical pattern for a sensor having a plurality of pairs of electrodes is shown in FIG. 3, wherein two branches and 10' of cm. length are shown as being provided and serve as a cathode and an anode for the sensor 6. If the gap distance between the electrodes is set by example to be 0.4 mm. and the maximum electrical resistance for actuating the sensor 6 is set by example to be 1 M0, then the sensor will thereby be actuated, when the glass plate is slightly blurred (cloudiness is observed).

If the gap distance between the electrodes is set to 0.8' mm. the sensor 6 wil be actuated, when the glass plate is moderately blurred (water drops are observed on the glass plate). By still further example, if the gap distance between the electrodes is set to be 1.6 mm. then the sensor 6 will be actuated when the glass plate is very blurred (continuous water drops are observed on the glass plate).

In view of the above, it is especially preferable to have the gap distance of the electrodes in the sensor substantially in the range of 0.4 1.2 mm.

It should be understood that while the sensor 6 has been shown in FIGS. 2 and 3 as having a particular shape that the invention is not so limited and the same can be of various shapes which are capable of detecting a change of electric current or impedance between the gap of the electrodes in response to a condensing of moisture on the surface of the glass plate.

Thus, for example, it is possible to use electrodes each of which are attached to a bus bar and have a plurality of branches. Likewise, it is possible to use electrodes having a curved or bent shape.

The electrodes 9 and 9 can be electric resistance wires, electroconductive lines or strips having a suitable electric resistance. It is especially preferable to use electrodes having high adhesiveness, high mechanical strength and chemical stability.

Generally, electrodes made of metals having metal ions which can easily migrate from an anode electrode to a cathode electrode and thereby result in an electrical short circuit when moisture is condensed in the gap of electrodes are not suitable. Thus, when electrodes made of metal are used, as the metal ions migrate from an anode electrode to a cathode electrode, the metal will be deposited on the cathode and after a long period of time will increase towards the direction of the anode electrode so as to cause an electrical short circuit and thereby render the sensor inoperable.

Accordingly, it is preferable to use electrodes made of metals which have non-migrative ions, such as Au, Pd, Pt and mixtures thereof, mixtures of such metals and glass frit, electroconductive metal oxides, such as RuO,, SnO,, In,0 and the like or mixtures of such metal oxides as glass frit.

The following is a typical example as an electrode used as the sensor.

100 parts by weight of finely crushed RuO, powder having an average particle diameter of 41.4. is uniformly admixed with 61 parts by weight of glassfrit having an average particle diameter of 1.4p. and which consists of 74.0 wt of PbO, 10.9 wt A 0 10.8 wt% of B,O and 3.82 wt% of SiO,. 39 parts by weight of an organic solvent of butyl carbitol acetate is then further added and kneaded at 25 C at 10 rpm..to thereby result in 15,700 cps of paste. The resulting paste is=-v screen-- printed onthe glass plate by using a silk screen in a pattern such as is shown in FIG. 3, and is dried at approximately 200 C in air for 10 minutes, and then heated at approximately 600 C, 650 C or 700 C for 3 minutes, so as to thereby form the moisture detecting electrodes.

The area of resistance of the electrode may be 60 ohms per square inch. It has been found preferable to use electrodes made of 50 wt percent of RuO, and substantially 50 10 wt percent of glass frit.

In order to detect a small amount of condensed moisture inthe vicinity of the gap of the electrodes9 and 9 of the sensor 6, it is preferable to form a moisture de tecting sensitivity amplifying region 12 on the surface of the glass plate 1, as shown in FIG. 2. The moisture detecting sensitivity amplifying region 12 can be fonned by grinding the surface of the glass-plate 1. by a conventional sandblast method, or by imparting hydrophilic properties bycoating or treating with a hydrophilic material, such as a synthetic resin. The electrodes-of the sensor are preferably printed or coated on the moisture detecting sensitivity amplifying region 12.

In operation, when no moisture is condensed within the gapof the electrodes 9 and 9 on the glass plate 1, the sensor 6 will not be electrically connected and thereby an open circuit is formed. When moisture is condensed so as to form a water film within the gap, of

the electrodes 9 and 9 the sensor 6 will be electrically closed by the water film so as to provide a closed circuit. The detecting circuit 7. serves to detect any change in the electric current within the gap between the electrodes 9 and 9. Thus, when no water film is formed on the sensor, the detecting circuit 7 will be opened and the detected electric current will be zero. However, in the presence of water, a predetermined amount of electric current will be supplied in the gap between the electrodes and if a sufficient level of water is present, thee detecting circuitwill be closed by a relay, such as a diode and a thyristor, whereby the control circuit 8 will supply an electric current through the bus bars 3 and 3' to the electric heating elements 2 for heating the same to provide a defogging effect on the glass plate 1.

It should be understood that the maximum electrical resistance of the sensor 6 used for detecting moisture can be selected in the range of substantially 100 KO to IOMQ depending on the resistance of the moisture condensed on the glass plate 1.

It should be further understood that when the moisture detecting sensitivity amplifying region 12 is provided that even though a small amount of moisture is condensed, water drops will not be formed, but instead of continuous water film will be formed. As such, an electric current is supplied within the gap between th electrodes 9 and 9', such that a small amount of water can be detected with high sensitivity as a change of electric current or impedance between the electrodes.

Moreover, when the moisture detecting sensitivity amplifying region 12 is prepared by applying a hydrophilic material or the like, the water condensed on the region will be spread over the entire area thereof because of the decrease in the surface tension of the water, such that a thin water film is formed, instead of water drops, and such that the sensitivity of the sensor 6 is greatly increased. As stated above it should now be apparant that when the moisutre detecting sensitivity amplifying region is formedon the glass platel that any water which could cause cloudiness of the glass plate and thereby obstruct visibility can be detected with high sensitivity. It is therefore especially preferable to form the moisture detecting sensitivity amplifying region together with the electrodes as a sensor.

It should also be understood that when the sensitivity amplifying region is formed at the position of the sensor, a constant sensitivity can be provided, even though the surface is not clean. I

By way of example, when the sensor having the typical pattern shown in FIG. 3 is provided, the anode and cathode branches are of 26 cm. in distance, the sensitivity amplifying region is formed by sand-blasting, and the maximum electrical resistance for actuating the sensor is set at 1 MO, it was found that if the gap between the electrodes was set to 0.4 mm that the sensor woule actuate just before the glass plate began to blur (no cloudiness is observed). It was'found that if the gap between the electrodes was set to 0.8 mm that the sensor would actuate when the glass plate was slightly blurred (cloudiness is observed). It was found that if the gap between the electrode was set to 1.6 mm that the sensor would actuate when the glass plate was very blurred (complete cloudiness is observed).

It should now be apparant that in accordance with the defogging glass plate of this invention, when cloudiness is formed on a glass plate by moisture or the like, the same is automatically detected by a sensor device whereby electric heating elements provided on the glass plate are automatically heated to immediately remove any such cloudiness formed.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A defogging glass plate which comprises an electric heating element mounted in contact with said glass plate and adapted to be coupled to a source of electric power,

a sensor having a plurality of electrodes which are arranged in parallel with gaps therebetween and which are fitted on the surface of said glass plate for automatically detecting any formation of a water, film within said gaps,

I a detecting electric circuit means coupled to said sensor and to said electric heating elementfor detecting a change of electric current due to the change of impedance within said gaps between said electrodes and for controlling the application of power from said source to said electric heating element when a water film is formed within said gaps; and, a moisture detecting sensitivity amplifying means formed on said glass plate in the region of said electrode gaps for enhancing the sensitivity of said detecting circuit means.

2. A defogging glass-plate as in claim 1, wehrein said moisture detecting sensitivity amplifying means is a sand blasted region onsaid glass plate.

3. A defogging glass-plate as in claim 1, wherein said moisture detecting sensitivity amplifying means is a regionwherein a hydrophilic material is applied to said glass plate. I

4. A defogging glass-plate as in claim 4 wherein said electrodes of said sensor are a calcinated composition formed by printing a composition of glass frit and RuO,. I I

5. A defogging glass-plate of claim 4, wherein said electrodes are made of substantially 50 percent by weight of RuO, and of substantially 50- 10 percent by weight of glass frit.

l F i 

1. A defogging glass plate which comprises an electric heating element mounted in contact with said glass plate and adapted to be coupled to a source of electric power, a sensor having a plurality of electrodes which are arranged in parallel with gaps therebetween and which are fitted on the surface of said glass plate for automatically detecting any formation of a water film within said gaps, a detecting electric circuit means coupled to said sensor and to said electric heating element for detecting a change of electric current due to the change of impedance within said gaps between said electrodes and for controlling the application of power from said source to said electric heating element when a water film is formed within said gaps; and, a moisture detecting sensitivity amplifying means formed on said glass plate in the region of said electrode gaps for enhancing the sensitivity of said detecting circuit means.
 2. A defogging glass-plate as in claim 1, wehrein said moisture detecting sensitivity amplifying means is a sand blasted region on said glass plate.
 3. A defogging glass-plate as in claim 1, wherein said moisture detecting sensitivity amplifying means is a region wherein a hydrophilic material is applied to said glass plate.
 4. A defogging glass-plate as in claim 4 wherein said electrodes of said sensor are a calcinated composition formed by printing a composition of glass frit and RuO2.
 5. A defogging glass-plate of claim 4, wherein said electrodes are made of substantially 50 - 90 percent by weight of RuO2 and of substantially 50- 10 percent by weight of glass frit. 